path: root/Documentation/scsi/53c700.txt
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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/scsi/53c700.txt
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+General Description
+This driver supports the 53c700 and 53c700-66 chips. It also supports
+the 53c710 but only in 53c700 emulation mode. It is full featured and
+does sync (-66 and 710 only), disconnects and tag command queueing.
+Since the 53c700 must be interfaced to a bus, you need to wrapper the
+card detector around this driver. For an example, see the
+NCR_D700.[ch] or lasi700.[ch] files.
+The comments in the 53c700.[ch] files tell you which parts you need to
+fill in to get the driver working.
+Compile Time Flags
+The driver may be either io mapped or memory mapped. This is
+selectable by configuration flags:
+define if the driver is memory mapped.
+define if the driver is to be io mapped.
+One or other of the above flags *must* be defined.
+Other flags are:
+define if the chipset must be supported in little endian mode on a big
+endian architecture (used for the 700 on parisc).
+allocate consistent memory (should only be used if your architecture
+has a mixture of consistent and inconsistent memory). Fully
+consistent or fully inconsistent architectures should not define this.
+Using the Chip Core Driver
+In order to plumb the 53c700 chip core driver into a working SCSI
+driver, you need to know three things about the way the chip is wired
+into your system (or expansion card).
+1. The clock speed of the SCSI core
+2. The interrupt line used
+3. The memory (or io space) location of the 53c700 registers.
+Optionally, you may also need to know other things, like how to read
+the SCSI Id from the card bios or whether the chip is wired for
+differential operation.
+Usually you can find items 2. and 3. from general spec. documents or
+even by examining the configuration of a working driver under another
+operating system.
+The clock speed is usually buried deep in the technical literature.
+It is required because it is used to set up both the synchronous and
+asynchronous dividers for the chip. As a general rule of thumb,
+manufacturers set the clock speed at the lowest possible setting
+consistent with the best operation of the chip (although some choose
+to drive it off the CPU or bus clock rather than going to the expense
+of an extra clock chip). The best operation clock speeds are:
+53c700 - 25MHz
+53c700-66 - 50MHz
+53c710 - 40Mhz
+Writing Your Glue Driver
+This will be a standard SCSI driver (I don't know of a good document
+describing this, just copy from some other driver) with at least a
+detect and release entry.
+In the detect routine, you need to allocate a struct
+NCR_700_Host_Parameters sized memory area and clear it (so that the
+default values for everything are 0). Then you must fill in the
+parameters that matter to you (see below), plumb the NCR_700_intr
+routine into the interrupt line and call NCR_700_detect with the host
+template and the new parameters as arguments. You should also call
+the relevant request_*_region function and place the register base
+address into the `base' pointer of the host parameters.
+In the release routine, you must free the NCR_700_Host_Parameters that
+you allocated, call the corresponding release_*_region and free the
+Handling Interrupts
+In general, you should just plumb the card's interrupt line in with
+request_irq(irq, NCR_700_intr, <irq flags>, <driver name>, host);
+where host is the return from the relevant NCR_700_detect() routine.
+You may also write your own interrupt handling routine which calls
+NCR_700_intr() directly. However, you should only really do this if
+you have a card with more than one chip on it and you can read a
+register to tell which set of chips wants the interrupt.
+Settable NCR_700_Host_Parameters
+The following are a list of the user settable parameters:
+clock: (MANDATORY)
+Set to the clock speed of the chip in MHz.
+base: (MANDATORY)
+set to the base of the io or mem region for the register set. On 64
+bit architectures this is only 32 bits wide, so the registers must be
+mapped into the low 32 bits of memory.
+pci_dev: (OPTIONAL)
+set to the PCI board device. Leave NULL for a non-pci board. This is
+used for the pci_alloc_consistent() and pci_map_*() functions.
+dmode_extra: (OPTIONAL, 53c710 only)
+extra flags for the DMODE register. These are used to control bus
+output pins on the 710. The settings should be a combination of
+DMODE_FC1 and DMODE_FC2. What these pins actually do is entirely up
+to the board designer. Usually it is safe to ignore this setting.
+differential: (OPTIONAL)
+set to 1 if the chip drives a differential bus.
+force_le_on_be: (OPTIONAL, only if CONFIG_53C700_LE_ON_BE is set)
+set to 1 if the chip is operating in little endian mode on a big
+endian architecture.
+chip710: (OPTIONAL)
+set to 1 if the chip is a 53c710.
+burst_disable: (OPTIONAL, 53c710 only)
+disable 8 byte bursting for DMA transfers.